A short course of HIV pre-exposure prophylaxis (PrEP) taken before and after sexual activity appears to significantly reduce the risk of HIV infection among high-risk men who have sex with men (MSM), according to an interim analysis of data from a major clinical trial. The findings were deemed to be so convincing that the study -- known as ANRS IPERGAY and based in France -- will be unblinded and all participants offered tenofovir/emtricitabine (Truvada), according to an announcement posted Oct. 29 on the study's official website.